Here's a simple house rule I'm using while running The Cleansing of Cameth Brin (see elsewhere on these forums).

The S&W Core Rules give characters a chance to hear sounds, force open stuck doors, find secret doors and traps, etc. The rules assume the use of 1d6 and the chances are expressed as x-in-6. In Cameth Brin, some secret doors and traps are easier or more difficult to discover than normal. I simulate this by using "variable task dice", as follows:

For example, when a secret door is described in the text as "Hard to find", a character who is searching in the right area has a 2-in-8 chance to find it, not 2-in-6. (An elf's chance becomes 4-in-8 if searching, or 1-in-8 if not searching.)

Additionally, I have house ruled Thieving Skills, ditching the percentages and using 1d6 (default) to resolve skill checks. The Hear Sounds column of Table 10: Thieving Skills gives the chances for all Thieving Skills except Climb Walls, which starts at 5 in 6. This makes thieves better at their job (a good thing in my book) and is compatible with the variable task dice rule described above.

I don't use this method for doors/traps/noise but I think it is a good way to handle variable difficulty and lend some variety to play. I may try it and see how it works. I'm also all for ditching the percentage thief checks - I've never liked them and also prefer d6-based checks. The only catch is that I think d6 works best in WB where level 10 is the cap, for core or complete I would switch to 2d6 checks to allow a greater range (see AS&SH for a good example of how this would work). On the other hand, how many campaigns get up above level 10 anyway? So maybe it doesn't matter.

Thanks for the input! Apart from some of the classic high-level Gygax modules back in the day (for which we just rolled up PCs of the appropriate levels) I've never played above level 7 or 8, and have no particular desire to do so. I think PCs ought to retire around level 9, and their players ought to be congratulated on having essentially "won" the game.

That said, even if you're playing high-level games, I think x-in-6 still works if the variable task dice rule is used. Consider: a thief of 11th level or above has a Thieving Skill of 6-in-6. It means she can breeze through Easy and Normal locks, etc. (she's a master thief after all) but she might still break sweat over a Hard lock (6-in-8) or be frustrated by an Extremely Hard one (6-in-12 or 50%; just like being a 1st-level apprentice again!)

I take the point, however, that x-in-6 doesn't allow for much in the way of "granularity". My preferred option for Thieving Skills in S&W is simply to use the Saving Throw number as a target. No "dead levels" and you can dispense with the Thieving Skills table entirely. For the Cameth Brin game, though, I wanted to try something different. Of course, none of my players has elected to play a thief, and now Finglas is waltzing around with a wand of secret door and trap detection, so the rule isn't seeing very much use anyway.